The overall objective of this proposed research is to further elucidate the cellular mechanisms by which salivary exocrine cells synthesize, store, and release their secretory components and thereby regulate the quality and quantity of the salivary secretions. In vivo and in vitro experiments using isotopically labelled amino acids will be used to study the mechanisms by which secretory proteins are synthesized and segregated within the membrane-bound spaces of the parotid exocrine cells. Intermediate events in the secretory cycle of these cells, such as the concentration of secretory contents within the immature secretory granule, and the production of secretory granule membranes will be investigated by assessing the possible role of sulfated polyanions or calcium binding as mechanisms for reduction of colligative properties within the secretory granule, and by analyzing the pattern of synthesis of the secretory granule membrane proteins. The events leading to exocytosis of the secretory contents will be investigated by exploring the sites of protein kinase activity in these cells and the relation of protein phosphorylation to release of secretory contents. The research has important implications concerning the role of the salivary secretions in maintenance of oral health.